1. Field of the Invention
The present invention relates to devices and methods for brachytherapy, and more particularly to devices and methods for treating macular degeneration and/or ocular melanoma using radiation therapy.
2. Description of the Related Technology
Macular degeneration is a common disease that is the leading cause of legal blindness among older people in the United States and Europe. Macular degeneration is believed to affect about 10% of those between the ages of 65 and 75 and about 30% of those between the ages of 75 and 85. Macular degeneration, wet type, is commonly caused by excessive growth of neovascular tissue to provide blood supply to oxygen-deprived retinal tissue. There is currently no known treatment for the dry type of macular degeneration. However, the neovascular tissue is very delicate and thus the blood vessels contained therein break easily, causing bleeding and damage to surrounding tissue, which often leads to macular degeneration.
Modern attempts to alleviate the effects of macular degeneration have included laser and surgical techniques. Although burning the retinal membrane with a laser has been effective in temporarily controlling the growth of neovascular tissue, the capillaries in the tissue tend to resume their growth in about three to four months following laser surgery, thereby requiring additional laser treatments until the laser treatments eventually become ineffective. Laser burning techniques are also known to destroy more cone cells, in some cases, than are destroyed by macular degeneration, which is counterproductive.
Surgery, on the other hand, has proven to be successful in removing neovascular tissue without substantially affecting the cone cell population. However, even the best surgical techniques merely postpone the growth of the vessels in the neovascular tissue for about two or three months, after which, more vessels grow into the scarred neovascular tissue and the patient must return for more surgery. Also, surgery has the disadvantage that it may cause more trauma to surrounding tissue than, for example, brachytherapy.
Radiation therapy has been attempted to treat macular degeneration. For example, U.S. Pat. No. 5,637,073 to Freire discloses a device, which is useful in treating macular degeneration. The proximal end portion of the device of Freire includes a handle and the distal end portion includes a wand having a cavity located at its distal tip to hold a radioactive material such as 90Sr. Unfortunately, the device of Freire suffers several drawbacks such as failing to provide a uniform radiation dosage to the treatment volume, which can easily result in over- or under-dosing the treatment volume. The use of 90Sr can also result in a large surface dose to the sclera immediately in contact with the applicator.
Accordingly, there is still a need for an improved radiation therapy device for providing a substantially uniform radiation dosage to the treatment area.
There is also a need for an improved radiation therapy device for the treatment of disorders such as macular degeneration and/or ocular melanoma.
There is also a need for improved methods to treat macular degeneration and/or ocular melanoma using radiation.